Dell Optiplex 3050 Intermittent USB Issues

Several Optiplex 3050s in my deployment have a USB issue where a mouse or keyboard will stop working. They also won't work after being plugged into a different USB port or after restarting the PC. The only "fix" I've found is to unplug everything from USB, restart the computer, wait for Windows to load, and then plug everything back in. This seems to work for a few days before the problem comes back. 

Does anyone know of a fix for this?

Thanks!